Prepaid Expenses and Other Assets - Additional Information (Detail) - Partnership Agreement [Member] - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2016	Jun. 30, 2019
Prepaid expenses and other assets [Line Items]
Partnership agreement			10 years
Upfront cash payment			$ 10.0
Prepaid expenses and other assets	$ 1.0			$ 1.0
Other assets, noncurrent	5.0			$ 5.3
Amortization expense	$ 0.3	$ 0.3